Other degenerative diseases of nervous system, not elsewhere classified (G31) ICD-10-CM
The G31 code range covers other degenerative diseases of nervous system, not elsewhere classified with 17 ICD-10-CM diagnosis codes. 14 of them are billable and valid for claim submission in fiscal year 2026, and the category headers group them but cannot themselves be billed.
Use Additional Code
The “use additional code” indicates that a secondary code could be used to further specify the patient’s condition. This note is not mandatory and is only used if enough information is available to assign an additional code.
- code, if applicable, for codes G31.0 G31.83 G31.85 G31.9
- dementia with anxiety F02.84 F02.A4 F02.B4 F02.C4
- dementia with behavioral disturbance F02.81 F02.A1 F02.B1 F02.C1
- dementia with mood disturbance F02.83 F02.A3 F02.B3 F02.C3
- dementia with psychotic disturbance F02.82 F02.A2 F02.B2 F02.C2
- dementia without behavioral disturbance F02.80 F02.A0 F02.B0 F02.C0
- mild neurocognitive disorder due to known physiological condition F06.7
Type 2 Excludes
A type 2 excludes note represents "Not included here". An excludes2 note indicates that the condition excluded is not part of the condition represented by the code, but a patient may have both conditions at the same time. When an Excludes2 note appears under a code, it is acceptable to use both the code and the excluded code together, when appropriate.
- Reye's syndrome G93.7
Codes in the G31 Range 17 codes · 14 billable
- G31 Other degenerative diseases of nervous system, not elsewhere classifiedNon-billable
- G31.0 Frontotemporal dementiaNon-billable
- G31.01 Pick's disease
- G31.09 Other frontotemporal neurocognitive disorder
- G31.1 Senile degeneration of brain, not elsewhere classified
- G31.2 Degeneration of nervous system due to alcohol
- G31.8 Other specified degenerative diseases of nervous systemNon-billable
- G31.80 Leukodystrophy, unspecified
- G31.81 Alpers disease
- G31.82 Leigh's disease
- G31.83 Neurocognitive disorder with Lewy bodies
- G31.84 Mild cognitive impairment of uncertain or unknown etiology
- G31.85 Corticobasal degeneration
- G31.86 Alexander disease
- G31.87 Primary progressive apraxia of speech New
- G31.89 Other specified degenerative diseases of nervous system
- G31.9 Degenerative disease of nervous system, unspecified
Clinical Terms in This Code Range
Definitions from the National Library of Medicine for conditions coded in the G31 range.
Alexander Disease
Rare leukoencephalopathy with infantile-onset accumulation of Rosenthal fibers in the subpial, periventricular, and subependymal zones of the brain. Rosenthal fibers are GLIAL FIBRILLARY ACIDIC PROTEIN aggregates found in ASTROCYTES. Juvenile- and adult-onset types show progressive atrophy of the lower brainstem instead. De novo mutations in the GFAP gene are associated with the disease with propensity for paternal inheritance.
Corticobasal Degeneration
Rare progressive neurological disorder characterized by Parkinsonism, cortical atrophy of multiple areas of the brain including the cerebral cortex and the basal ganglia, cognitive dysfunction and eye movement abnormalities.
Frontotemporal Dementia
The most common clinical form of FRONTOTEMPORAL LOBAR DEGENERATION, this dementia presents with personality and behavioral changes often associated with disinhibition, apathy, and lack of insight.
Frontotemporal Lobar Degeneration
Heterogeneous group of neurodegenerative disorders characterized by frontal and temporal lobe atrophy associated with neuronal loss, gliosis, and dementia. Patients exhibit progressive changes in social, behavioral, and/or language function. Multiple subtypes or forms are recognized based on presence or absence of TAU PROTEIN inclusions. FTLD includes three clinical syndromes: FRONTOTEMPORAL DEMENTIA, semantic dementia, and PRIMARY PROGRESSIVE NONFLUENT APHASIA.
Lewy Body Disease
A neurodegenerative disease characterized by dementia, mild parkinsonism, and fluctuations in attention and alertness. The neuropsychiatric manifestations tend to precede the onset of bradykinesia, MUSCLE RIGIDITY, and other extrapyramidal signs. DELUSIONS and visual HALLUCINATIONS are relatively frequent in this condition. Histologic examination reveals LEWY BODIES in the CEREBRAL CORTEX and BRAIN STEM. SENILE PLAQUES and other pathologic features characteristic of ALZHEIMER DISEASE may also be present. (From Neurology 1997;48:376-380; Neurology 1996;47:1113-1124)
About the G31 Code Range
The ICD-10 code section G31 covers a variety of other degenerative diseases of the nervous system not classified elsewhere. These codes are used for diagnosing less common or specific neurological disorders that involve progressive nerve damage and loss of brain function.
This section includes important conditions such as G31.0 frontotemporal dementia, and its specific forms like G31.01 Pick's disease, which is known for symptoms including behavioral changes and language difficulties. Pick's disease is also referred to by synonyms like "Progressive aphasia" or "Dementia due to Pick's disease," helping coders identify it precisely. G31.09 captures other frontotemporal neurocognitive disorders, including familial and genetic variants. The codes also cover degeneration due to alcohol (G31.2), neurocognitive disorder with Lewy bodies (G31.83), and mild cognitive impairment of unclear cause (G31.84). Rare hereditary disorders such as Leigh’s disease (G31.82) and Alexander disease (G31.86) are included as well. For unspecified or mixed presentations, G31.8 and G31.9 offer coding options. Using the appropriate ICD-10 code for degenerative nervous system disease ensures accurate diagnosis and treatment planning for these complex neurological conditions.
Questions About This Page
How many billable codes are in the G31 range?
Of the 17 codes in this range, 14 are billable and valid for claim submission from October 1, 2025 through September 30, 2026. Category header codes group them but cannot be reported on claims.
What does the G31 range classify?
The range classifies other degenerative diseases of nervous system, not elsewhere classified. Each code links to its own reference page with billing status, MS-DRG grouping, coding notes, and clinical information.
Related References
Source: CMS FY 2026 ICD-10-CM Tabular List and order file, effective October 1, 2025 through September 30, 2026.
